The effect of chloroquine on strips of pregnant human myometrium

We investigated the effect of chloroquine on the activity of strips of myometrium obtained at lower segment Caesarean sections from 150 patients. At concentrations below 1 X 10(-4) M, chloroquine did not affect the frequency, tonus or amplitude of contraction. At higher concentrations, it more than doubled the frequency of contractions in muscle strips showing spontaneous activity. In quiescent strips requiring stimulation by oxytocin, chloroquine had a generally depressant effect which could be overcome by higher doses of oxytocin. We suggest that chloroquine does not cause premature labour or abortions.